This disclosure relates to processes for preparing latex emulsions. More specifically, continuous processes for emulsion polymerization are described. These processes can be used to produce a latex suitable for use in the preparation of toner compositions.
Processes for forming toner compositions for use with electrostatographic, electrophotographic, or xerographic print or copy devices have been previously disclosed. For example, toners can be prepared by a process that involves emulsion preparation, followed by aggregation and coalescence of the emulsion, washing the resulting product, and then isolating the toner.
Methods of preparing an emulsion aggregation (EA) type toner are known and toners may be formed by aggregating a colorant with a latex polymer formed by batch or semi-continuous emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex by first forming a seed polymer. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,370,963, 5,344,738, 5,403,693, 5,418,108, 5,364,729, 5,346,797, and U.S. patent application Ser. No. 11/155,452 filed on Jun. 17, 2005 entitled “Toner Processes”, the disclosures of each of which are hereby incorporated by reference in their entirety. Other processes are disclosed in U.S. Pat. Nos. 5,348,832, 5,405,728, 5,366,841, 5,496,676, 5,527,658, 5,585,215, 5,650,255, 5,650,256 and 5,501,935, the disclosures of each of which are hereby incorporated by reference in their entirety.
As noted above, latex polymers utilized in the formation of EA type toners may be formed by batch or semi-continuous emulsion polymerization. Where a batch process is utilized, because the individual batch process involves the handling of bulk amounts of material, each process takes many hours to complete before moving to the next process in the formation of the toner, that is, aggregation and/or coalescence. In addition, batch-to-batch consistency is frequently difficult to achieve because of variations that may arise from one batch to another. While semi-continuous polymerization may reduce the time required to proceed to aggregation and/or coalescence, it still can be difficult to achieve consistency in the product because of variations which can arise from one emulsion to another.
Spinning disc reactors (SDR) are known. The spinning disc concept for reactors attempts to apply process intensification methods within the fields of heat and mass transfer. The technology was developed for heat and mass transfer operations such as heat exchanging, heating, cooling, mixing, blending and the like, for example, as disclosed by Jachuck et al., “Process Intensification: The Opportunity Presented by Spinning Disc Reactor Technology,” Inst. Chem. Eng. Symp. Ser. 1997, Vol. 141, pp. 417-424. The technology operates by the use of high gravity fields created by rotation of a disc surface causing fluid introduced to the disc surface at its axis to flow radially outward under the influence of centrifugal acceleration in the form of thin, often wavy, films. Such thin films exhibit excellent heat and mass transfer rates.
It would be advantageous to provide a process for the preparation of a latex resin suitable for use in a toner product that is more efficient, takes less time, and results in a consistent toner product.